This invention relates to a roof machine for the electrostatic coating of the front end, roof and rear surfaces of an automobile chassis. Such roof machines are known and used in the painting lines of automobile plants.
The known roof machines generally comprise an elongated, box-like roof beam, which is located transversely over the conveyor belt within the spraying compartment and is suspended in the center of the roof in such a manner that it can be lowered and raised. A similar beam-like support for the atomizers hangs by means of arms on the bottom side of the roof beam, such that this holding beam can be reciprocated horizontally relative to the actual roof beam (pendulum motion) and can be rotated around its horizontal axis. All supply elements for the atomizers, namely the metering pumps, the control and changeover valves for the paint, and the pneumatic valves, and the drive motors and gears for the pendulum and rotating movements of the holding beam as well are housed in the roof beam, and in many cases also the drive motor for the up-and-down movement of the roof beam itself. The result is that the known roof beams are heavy and voluminous, a feature that not only requires very rigid roof constructions and strong drive motors for the beam movement but also induces, above all, significant flow turbulences in the spraying compartments. As well-known, such spraying compartment are continuously ventilated, the ventilation being achieved in that fresh air, which is supposed to flow from top to bottom as uniformly and linearly as possible through the spraying compartment, where the fresh air is delivered together with paint and solvent vapors, is supplied through openings distributed over the entire coiling of the spraying compartment. However, the roof beams, which are normally large in size for the aforementioned reasons, represent at this stage a signficant flow impedance, which, as smoke tests have demonstrated, generates significant turbulences, a feature that is extremely disadvantageous for the uniformity of the coating process. Additional disturbing factors for a uniform air flow constitute the hose bundles leading from the actual roof beam to the atomizer holding beam. Finally, it has been demonstrated that the many components carrying out the mechanical movements and located in the roof beam are a source of dust and lubricant vapors that may not be overlooked, given that during the painting of an automobile chassis it is important that the process be free of dust and lubricant vapors.